The present invention relates to a surveying system for searching a target and for automatically performing a collimation.
The survey operation is performed using a survey instrument positioned at a reference point and a collimation target (a reflection mirror, a corner cube, etc.) installed at a target point which is to be collimated by the survey instrument.
With the progress in an automation technique, the survey instrument is also under the influence of such a trend, and a survey operation is now generally practiced by an one-man operation.
A survey instrument thus automated comprises an angle detector for measuring a direction of the collimation, and a light wave survey instrument for measuring the distance to a collimation target. Further, in order to achieve the survey operation under one-man control, it is provided with a tracking function for detecting and tracking the collimation target. In the survey operation under one-man control, an operator is positioned on collimation target side, and the collimation target is moved by the operator depending on a working process. When the operator moves the collimation target, the survey instrument tracks the collimation target and automatically collimates the collimation target.
Once the survey instrument has collimated the collimation target, the collimation target is automatically tracked. In this case, the range of collimation is limited to a range of visual field of a telescope of the survey instrument. Therefore, when the collimation target is moved, and if the collimation target is moved at such speed that tracking can be performed, tracking can be carried out without any problem. However, if the moving speed is higher than the speed, at which tracking can be performed or in case the collimation target is beyond the visual field of the telescope, tracking cannot be performed. Or, in case the visual field is temporarily interrupted by some obstacle, no tracking can be carried out. When tracking cannot be performed, similarly to the case where the collimation target is collimated for the first time, the survey instrument is rotated approximately over total circumference to search the collimation target.
To search the collimation target, the survey instrument is rotated over total circumference, and a reflection beam of the laser beam from the survey instrument reflected by the collimation target is detected by the survey instrument.
When the survey instrument searches the collimation target, the reflection beam from the collimation target must be detected by the telescope. However, the visual field of the telescope is narrow, and the survey instrument main unit must be rotated repeatedly over total circumference while changing the vertical angle. It is necessary to frequently perform the searching of the collimation target, not only in the first collimation in the survey operation but in the middle of surveying process from the reasons as described above. Because it takes much time for the searching of the collimation target at present, it is very important to search the collimation target within short time and in an efficient manner in order to increase working efficiency in the survey operation under one-man control.
When we consider the guide light entering the survey instrument, not only the guide light directly entering from the collimation target, but also the guide light reflected by an optical system after entering the survey instrument is included in it. Further, the light other than the guide light is also included. The light and beam reflected by the optical system is turned to noise, and S/N ratio is decreased. When S/N ratio is low or when S/N ratio is changed due to the light receiving condition, an amplification factor of a photodetection signal from a photodetection element must be changed to an optimal value. This causes such a problem that much time is required for the searching of the collimation target.
It is an object of the present invention to provide a system, by which it is possible to promptly detect a collimation target without rotating the survey instrument main unit over total circumference and to perform the searching of the collimation target within short time and in efficient manner. It is another object of the present invention to provide a system, by which it is possible to improve S/N ratio of the received reflection beam and to perform the collimation of the collimation target within the shortest time.
To attain the above objects, the surveying system according to the present invention comprises a survey instrument main unit for receiving and detecting a guide light projected from a collimation target, a horizontal rotating mechanism for rotating the survey instrument main unit in a horizontal direction, a control unit for controlling the horizontal rotating mechanism, a rough direction detecting unit capable to detect the guide light from all horizontal directions, and a precise direction detecting unit arranged in a direction to collimate the survey instrument main unit from a telescope and detects the guide light only in a range of a predetermined angle, wherein the control unit controls the horizontal rotating mechanism so that a direction of the survey instrument main unit is aligned to the collimation target based on a result of detection from the rough direction detecting unit, and collimates the survey instrument main unit to the collimation target based on a result of a detection from the precise direction detecting unit. Further, the present invention provides a surveying system as described above, wherein the precise direction detecting unit comprises a photodetection sensor, a photodetection limiting means for limiting a photodetection range in a horizontal direction of the photodetection sensor, and an optical means for converging the guide light at a position of the photodetection limiting means. Also, the present invention provides a surveying system as described above, wherein the optical means is a cylinder lens. Further, the present invention provides a surveying system as described above, wherein the optical means is a cylinder lens curved around a focal point thereof. Also, the present invention provides a surveying system as described above, wherein the photodetection limiting means is a mask arranged on a photodetection surface of the photodetection sensor. Further, the present invention provides a surveying system as described above, wherein the photodetection limiting means is a diaphragm plate arranged at a focal point of the optical means. Also, the present invention provides a surveying system as described above, wherein the photodetection limiting means further comprises a front stage diaphragm for cutting off reflection lights in the precise direction detecting unit. Further, the present invention provides a surveying system as described above, wherein the front stage diaphragm has a plurality of slits with size thereof gradually reduced toward a photodetection surface.